Effect of Ball Milling Parameters on the Refinement of Tungsten Powder

Abstract

The high-energy ball milling method was adopted to explore the influence of ball milling parameters, such as milling speed and additive amounts of process control agent (PCA) on tungsten powder. The morphology and microstructure of tungsten powder in the process of refinement were characterized by field-emission scanning electron microscope (FE-SEM), field-emission transmission electron microscope (FE-TEM), and X-ray diffractometer (XRD). Results revealed that the ball milling process and the refinement of tungsten particle and grain can be largely influenced by these two parameters. The milling efficiency was found to be highest with the milling speed of 700 rpm and additive amounts of 8% PCA. The mechanisms for the effect of these two parameters and milling time on the refinement process were discussed. Nanocrystalline tungsten powder with a particle size and grain size smaller than 100 nm was obtained, and the grain size of 5-15 nm was fabricated successfully under the highest milling efficiency conditions.

Influence of the Oxide and Ethanol Surface Layer on Phase Transformation of Al-Based Nanocomposite Powders under High-Energy Milling

“…In the case when one mills two different metallic powders, several solid phase transformations take place [12,13,14,15]. A process control agent (PCA) such as stearic acid, benzene, methanol, or ethanol is added to the powder mixture during milling to reduce the effect of cold welding between powder particles [16,17,18]. The PCA adsorbs on the surface of the powder particles and minimizes cold welding between powder particles and thereby inhibits agglomeration [19,20].…”

Effect of Rare Earth Metals (Y, La) and Refractory Metals (Mo, Ta, Re) to Improve the Mechanical Properties of W–Ni–Fe Alloy—A Review

“…This leads to segregation of impurities on the tungsten boundaries and formation of intermetallic precipitates during the sintering process. Some of the techniques, like using alloy-coated milling media with a protective atmosphere and using surfactants, can reduce the contamination effect [ 92 , 93 ].…”

Coated Metal Powders for Laser Powder Bed Fusion (L-PBF) Processing: A Review

“…Ball milling is a largely diffused technique that allows dispersing particles on metal powders: it is a non-equilibrium process generally operating at low temperatures, with conceptually linear operations, and a low overall cost [101,102]. The optimal control of the results obtained from ball milling is however nontrivial; plenty of variables such as ball size, rotation speed, duration, atmosphere, and process control agents (PCA) have significant effects on its outcomes.…”

“…PCA acts on powder's purity, grain size, and shape. The ball milling process can be both dry and wet depending on the necessity: in wet ball milling, a solution is added as PCA to reducing the maximum temperature reached during the process [101]. The general scheme of the ball milling process is reported in Figure 2; the metal powders and the coating particles are inserted into a mill containing the balls and the PCA if needed; the balls lead to a faster homogenization, promoting the adhesion of the coating particles to the powder.…”